1. Field of the Invention
This invention discloses solutions for cleaning plastic contact lense materials. Specifically it relates to aqueous solutions comprising a water-soluble peroxide, a catalytic amount of a transition metal salt, a surfactant, and optionally, a tonicity salt. These solutions effectively clean hard, flexible and soft hydrogel contact lenses.
Because of the environment in which contact lenses are handled and employed, a wide variety of materials may adhere to lenses. During wear, lenses are subjected to proteinaceous materials, particularly lysozymes and mucoproteins; and lipids such as sterols, waxes, glycerides, phospholipids, fatty alchols and acids. In addition to these naturally occurring materials, cosmetics, greases from the hands and dusts and other airborne and environmental materials can all act to form a strongly adhering lens coating.
Proteinaceous materials constitute the major amount of lens soils. They can also be difficult to remove completely and efficiently from plastic lens materials, particularly in the instance of hydrophilic hydrogel materials which can readily absorb lysozyme and mucoproteins. If lenses are not properly cleaned these proteinaceous materials and other soils can build up to a point where wearer comfort is affected, lens spectral characteristics are affected, sterilization becomes difficult or gas permeability may be decreased.
Physical characteristics of the various lens plastics vary widely, ranging from the structurally rigid, lipophilic, polymethyl methacrylate (PMMA) and PMMA-silicone materials to the flexible, hydrophilic, hydrogel polymers. Rigid polymerics can be mechanically scrubbed even though it may be most desirable to keep handling to a minimum to avoid scratching, breaking or otherwise mechanically damaging the lenses. Hydrogel polymers and other soft flexible lens materials cannot be mechanically scrubbed because they are easily torn or scratched. Therefore some non-mechanical means must be used to remove soil accretions.
Additionally, lenses must be sterilized to prevent transmission of pathogenic agents onto the eye. Certain lens polymers, particularly hydrogels, cannot be chemically sterilized because they absorb antimicrobial drugs which are also eye irritants, so alternative sterilization techniques such as heat in the form of boiling water or steam are often used. High temperatures don't clean lenses and in fact tend to accelerate lens soil buildup by precipitating absorbed proteinaceous materials. Sterile saline solutions have little if any effect on soil removal so some additional cleaning procedure is required. Peroxides alone are adequate disinfectants but do not adequately remove lens soils, particularly non-polar materials.
It is therefore desirable to find a simple and efficient one step procedure for cleaning contact lenses which will ensure the removal of all soils but especially proteinaceous material. The procedure should be usable with all contact lenses. The method should be effective over a relatively short period of time, certainly not longer than overnight, and should be safe to the user and provide a clean lens which may be readily rinsed and safe for introduction into the eye thereafter without further treatment.
2. Prior Art
Contact lens cleaning solutions utilizing peroxides are disclosed in U.S. Pat. Nos. 3,873,696, 3,829,329, 3,908,608 and British Pat. No. 2,03,03. Bleaching and cleaning solutions containing similar ingredients are set out in U.S. Pat. Nos. 3,991,000, 3,583,924, and 2,975,139. Contact lens cleaning solutions which utilize surfactants, particularly amphoteric surfactants, are disclosed in U.S. Pat. Nos. 4,104,187, 4,126,587, and 4,046,706.